1. Field of the Invention
The present invention relates to an apparatus for obtaining images of cornea endothelium, by which images of cornea endothelium cells of an eyeball of a subject person can be observed or photographed under magnification. More specifically, the invention relates to an apparatus for obtaining images of cornea endothelium, which apparatus is capable of detecting a cornea endothelium focused position by detecting weak cornea-endothelium reflected light with high accuracy and reliability, and also relates to an apparatus for obtaining images of cornea endothelium, which apparatus is capable of measuring cornea thickness with high accuracy by detecting epithelium reflected light with high accuracy.
For seeing influences of contact lenses or for medical examination and treatment before and after an operation of cataract, it is necessary to observe the state of cornea endothelium cells. Therefore, for observing or photographing under magnification cornea endothelium cells of an eyeball of a subject person, there have conventionally been used apparatus in which with an objective lens of a microscope of non-contact type or contact type with respect to the eyeball surface of the subject person, slit illumination light is applied toward an observation part obliquely of the eye axis, and its reflected light from the cornea is magnified, in which state the cornea endothelium cells can be observed, or in which apparatus an optimum imaging position where a TV camera or the like is focused on cornea endothelium is detected by the principle of the so-called triangulation method by detecting the position of the reflected light of the slit illumination light from the cornea endothelium, in which state the cornea endothelium cells of the subject part can be imaged by the TV camera or the like.
To solve these inconveniences in operation of the conventional apparatus, the present applicant has previously proposed an apparatus which is capable of automatically observing or photographing under magnification images of cornea endothelium cells of a subject part and moreover which is capable of measuring cornea thickness of the subject eye besides the observation and photographing under magnification, in Japanese Patent Application No. HEI 05-166132, filed Jun. 10, 1993. In this apparatus, for measurement of cornea thickness, one light receiving element has been used to detect two rays of reflected light from cornea epithelium and cornea endothelium.
However, in these conventional apparatus, the focusing on the cornea endothelium has been accomplished by manually moving a microscope frame, on which a TV camera is mounted, back and forth with the use of an operation member such as a joy stick. In this operation, since epithelium reflection is intense and endothelium reflection is weak with a large difference therebetween when the subject part is illuminated through a slit and the resulting cornea reflected light is used to obtain a focusing, it has been difficult to detect endothelium reflected light and therefore difficult to accomplish the focusing on the cornea endothelium, as a problem. As a result, considerable labors and skills would be needed to accomplish the focusing on the cornea endothelium cells of the subject part.
Another problem is that it has been difficult to detect both epithelium reflected light and endothelium reflected light reliably and correctly. Further, for measurement of the cornea thickness, there has still been a demand of accurately detecting epithelium reflection as well as endothelium reflection.